both provide equal backlinks to a site. if you need quality backlinks then try directory submission. because directory submission is a process where you submit your site url directly to other sites which has high page rank. one important thing about back links is that you cant submit your site url in all websites. you have chances to get your site penalized. your site url should be submitted to a site which is connected to your site in some way. so while submitting urls in websites which is related to your site helps you in getting good back links. so directory submission is the best way. you can either do it by yourself or you can get the assistance from providers. but all seo strategies are difficult to do it manually and it will take long time so it is better to get assistance from seo service providers who provides these for your site. i got the seo package for my site from
XnYnZ.com. they did all the seo services for my site instead of me.